1. Field of the Invention
The present invention relates to a debugging system and a debugging method, and more particularly, to a debugging system and a debugging method that allow debugging to be carried out in a state in which a target device is mounted in a target system.
2. Description of Related Art
In recent years, as a method of developing a program to be installed in a microcomputer (hereinafter, referred to as “micro”), there is known on-chip debugging that allows debugging to be carried out in a state in which a target device is mounted in a target system. To realize the on-chip debugging, there is a need to provide a debug interface dedicated to the target device. The debug interface is allocated to external terminals of the target device. Accordingly, it is necessary to reduce the number of debug interface terminals unnecessary for a user as much as possible. Further, in order to reduce costs for a development environment, it is necessary to obtain trace data in real time.
FIG. 7 shows a debugging system disclosed in Japanese Unexamined Patent Application Publication No. 11-282713 (Kudo et al.). A debugging system 70 includes a microcomputer 71 and a debug tool 72. A trace information output unit 73 provided in the micro outputs trace information to the debug tool from dedicated four terminals. In such a configuration, the debug tool 72 can obtain trace data in real time. Further, Japanese Unexamined Patent Application Publication No. 2006-268727 (Fuse et al.) discloses that on-chip debugging is realized using a single debug terminal as a debug terminal unnecessary for a user (see FIG. 8). Note that Japanese Unexamined Patent Application Publication No. 06-120929 (Ii) discloses an analog transmission circuit for transmitting multi-value data via an analog transmission line (see FIG. 9).
However, in the technologies disclosed in Kudo et al. and Fuse et al., it is difficult to realize the debug interface with a small number of terminals and to obtain trace data in real time. In other words, in the debugging system disclosed in Kudo et al., in order to obtain trace data in real time, there is a need to secure at least four debug interface terminals unnecessary for a user. On the other hand, in a debugging system disclosed in Fuse et al., the debug interface is realized with a single terminal. However, the debugging system is incapable of receiving trace data because it is necessary to transfer a large amount of data in receiving the trace data. Further, in the analog transmission circuit disclosed in Ii, two-way communication is not performed. Accordingly, in the analog transmission circuit, it is difficult to realize on-chip debugging which requires two-way data communication.
As described above, it has been difficult for conventional debugging systems to receive trace data with a small number of terminals in real time.